Syringe

ABSTRACT

A liquid syringe, particularly a microsyringe, of a type suitable for separating a trapped gas from a liquid, and for dispensing small, preselected, accurately measured quantities of the liquid specimen into a media, e.g., a G.C. or mass spectrograph. The syringe is characterized by a barrel, a tubular needle mounted on the forward end of the barrel and a reciprocable plunger mounted on the opposite end of the barrel. The bore through the needle and barrel are communicated one with the other, and the bore of the barrel is provided with an opening of cross-section larger than the cross-section of the bore forward of the enlarged opening. The enlarged opening permits separation of gas from a liquid specimen. By withdrawal of the forward end of the plunger rearwardly into this opening, gas enters into the enlarged opening, and on forward movement of the plunger the liquid is separated forward of the plunger tip and gas is transmitted rearwardly through the annulus between the plunger and inside wall of the barrel rearwardly of the enlarged opening.

United States Patent [191 Harris, Sr. et al.

[451 May 7,1974

[ SYRINGE [75] Inventors: Rano J. Harris, Sr.; Rano J. Harris,

Jr., both of Baton Rouge, La.

[73] Assignee: Precision Sampling Corporation,

Baton Rouge, La.

[22] Filed: July 18, 19.73

[21] Appl. No.: 380,461

[52] US. Cl.. 222/386, 128/218 P, 239/331 Primary Examiner-M. HensonWood, Jr. Assistant Examiner-Michael Y. Mar

[57] ABSTRACT A liquid syringe, particularly a microsyringe, of a typesuitable for separating a trapped gas from a liquid, and for dispensingsmall, preselected, accurately measured quantities of the liquidspecimen into a media, e.g., a G.C. or mass spectrograph. The syringe ischaracterized by a barrel, a tubular needle mounted on the forward endof the barrel and a reciprocable plunger mounted on the opposite end ofthe barrel. The bore through the needle and barrel are communicated onewith the other, and the bore of the barrel is provided with an openingof cross-section larger than the crosssection of the bore forward of theenlarged opening. The enlarged opening permits separation of gas from aliquid specimen. By withdrawal of the forward end of the plungerrearwardly into this opening, gas enters into the enlarged opening, andon forward movement of the plunger the liquid is separated forward ofthe plunger tip and gas is transmitted rearwardly through the annulusbetween the plunger and inside wall of the barrel rearwardly of theenlarged opening.

9 Claims, 5 Drawing Figures PATENTEUMAY 1 I914 3309.298

FIGJ

SYRINGE It has long been a desideratum in the art to provide a syringe,particularly a microsyringe, from which a trapped gas, e.g., air, can bereadily, and conveniently, expelled after having been filled with aliquid. Prior art liquid syringes thussuffer the disadvantage that theplunger generally has to be repeatedly reciprocated while the dispensingend of the needle thereof is maintained below the surface of the liquidspecimen being sampled to purge the needle and barrel of an occludedbubble, or bubbles, e.g., air. The penalty for failure to effectivelyeliminate the air results in error in the measurement of the actualvolume of liquid sample intended for injection, which source of errorcan be particularly significant in high precision microsyringes of thetype used for injection of very small and infinitesimal quantities ofaccurately measured liquid specimens into a media, e.g., modernanalytical instruments such as a mass spectrometer, gas chromatograph,and

.the like. The necessity for continued reciprocation of the plunger inattempts to eliminategas bubbles, in handling some typesof liquidspecimens, also creates emulsions. It also occasions increased plungerwear, and sometimes causes plunger damage and abrasion.

It is accordingly, a primary objective of the present invention toobviate these disadvantages and provide a new and improved syringe,particularly a microsyringe, capable of manual or automated use.

A specific object of the invention is to provide a syringe of suchcharacter which is particularly useful for the injection of liquidspecimens on the order of only about 0.01 to about 5 microliters, orfractional parts thereof.

A further object is to provide a syringe of the kind characterized whichis of simple construction, providing a device which can be readilymanufactured, is easy to use, and is conveniently disassembled forcleaning and maintenance.

These objects, and others, are provided by the novel apparatus of thepresent invention characterized as a liquid syringe, particularly amicrosyringe, wherein is included the usual barrel, a cannula or needlemounted or positioned in the forward end of the barrel, and areciprocable plunger mounted in the rearward end of the barrel. Thebarrel and needle are each formed by an enclosing wall, defining in eachmember an axial opening or bore, and the bore of the needle and barrelare communicated one with the other. The bore of the barrel is providedwith an enlarged open section toward the rearward portionthereof,throughwhich the forward end of the plunger travels, the portion of thebore forward of the said enlarged open section being of substantiallyuniform diameter. The outside diameter of the forward endof the plungeris substantially equal to the inside diameter of the bore of the barrel(but smaller than said enlarged open section) within which the'rod orpiston is reciprocably mounted, or substantially equal to the insidediameter of both the barrel and needle within which the rod or piston isreciprocably mounted, wherein the path of travel of the plunger includes both the bores of the needle and barrel. In a preferred form, theforward end of the plunger is capped by a seal of external diameterapproximating the inside diameter of the barrel or the inside diameterof both the barrel and needle. In either form, the only path forsignificant ingress and egress of liquid into or from the 2 barrel isvia an opening at the dispensing end of th needle caused by positivemovement of the plunger.

' These and other salient features and advantages of the invention arefurther and more fully described by the following description whichmakes reference to the attached drawings.

Referring to the drawings:

FIG. 1 is a perspective view of a preferred type of liquid syringeembodying the present invention, and

FIGS. 2 through 5, showing the syringe of FIG. 1 in partial section,depict graphically a series of views describing the filling of thesyringe with a liquid specimen,

elimination of trapped air, and discharge of an accurately measuredquantity of the liquid specimen.

Referring to FIG. I there is illustrated, in perspective,

a syringe which includes a barrel 11 (of transparent character) formedby a sidewall which completely encloses a central axial opening or bore12. The external portion of the barrel 11, if desired, is suitablyscribed with indicia marks indicating volumetric measurements. Therearward portion of the axial opening or bore 12, it will be observed,is provided with an enlarged open portion or segment 13, the bore 12forward of enlarged segment 13 being of substantially uniform plunger 15is provided with a resilient cap or seal 16, 7

preferably of a type described by application Ser. No.

- 66,13 6, filed Aug. 21, 1970, the outside diameter of whichapproximates the inside diameter of the bore 12 forward of the enlargedopening 13. The rearward end of plunger 15, for convenience, is providedwith a thumb button 17.

The nature and function of the enlarged segment 13 of bore 12 ineliminating a trapped air bubble is described by reference to the seriesof views depicted by reference to FIGS. 2 through 5 Referring first toFIG. 2, the dispensing, or open, end 9 of hollow needle 14 is immersedin a source of liquid (not shown) and retraction of plunger 15 (ormovement of the plunger in the direction shown by the open arrow) isbegun. As

plunger 15 moves rearward, liquid passes through the opening at thedispensing end 9 of needle 14 and into the axial opening or bore of theneedle, with a small amount of air, and begins to fill the forward endof bore 12. Thus, it will be observed, as depicted in FIG. 1, that anair bubble 18 is trapped forward of plunger seal 16,

or between liquid 19 and plunger seal 16. The trapped reference to FIG.4, the plunger 15 is pushed forwardly into the enlarged opening 13 atwhich time the air is displaced through the annulus between the borerearward of the seal 16 and inside wall of the rearward segment of bore12. On continued forward movement of plunger 15, the seal 16 enters intothe bore 12 forward of the enlarged opening 13, such that only liquid islocated forward of the forward end of seal 16. A small residuum ofliquid may remain within the enlarged opening 16 which itself creates noerror in that-only the liquid forward of plunger seal 16 is measured andinjected. The cycle can be repeated ad infinitum.

It is apparent that various modifications and changes can be madewithout departingthe spirit and scope of the present invention. Thesyringe is constructed of materials substantially inert or nonreactiveto the chemical or corrosive action of the liquid specimens to bemeasured and dispensed. The barrel of the syringe is normallyconstructed of glass, but can be constructed of a plastic orplastic-like material. The needle and plunger are normally constructedof metal. The seal is constructed of a resilient material, generally aselflubricated type of plastic, and preferably polytetrafluoroethylenee.g., Teflon).

The enlarged opening within the bore must be of greater inside diameterthan the inside diameter of the bore forward of the said enlargedopening, and larger than the external diameter of the forward end of theplunger. Generally,'the inside diameter of the enlarged opening at thelocation of the largest part of the crosssection) ranges from about 1.25to about 2, and preferably from about 1.3 to about 1.75 times the insidediameter of the bore forward of the enlarged opening, on the other hand,is generally somewhat greater than the length of the plunger seal, wherea seal is employed. Generally, however, the length of the enlargedopening ranges no greater than about 1.5 to 2 times the length of theseal.

It is apparent that various changes, such as in the absolute or relativedimensions of the parts, materials used, and the like, can be madewithout departing the spirit and scope of the invention. Havingdescribed the invention, what is claimed is:

l. A syringe for use in separating trapped gas from liquid, and fordispensing small, 'pre-selected, accurately measured quantities of theliquid specimen into a media such as an analytical instrument,comprising the combination of a barrel formed by an enclosing side walldefining a central bore, the bore being of substantially uniformcross-section forward of an opening of enlarged cross-section within thebore located rear-.

wardly within the barrel,

a hollow needle mounted on the front end of the barrel, the bore ofwhich is in open communication with the bore through the barrel,

a plunger reciprocably mounted within the bore from the rearward end ofthe barrel, the forward end of the plunger being traversible through theenlarged opening within the bore, and within the bore of the barrelforward of the enlarged opening itself,

whereby gas trapped within a liquid to be dispersed can be separatedfrom the liquid, and a liquid specimen isolated from the gas formeasurement and ejection by withdrawal of the forward end of the plungerinto the enlarged opening within the bore of the barrel, whereupon byforward movement of the plunger the gas. is extruded through the annulusbetween the plunger and inside wall of the barrel rearwardly of theenlarged opening, and the liquid trapped for measurement and ejection byforward movement of the plunger.

2. The syringe of claim 1 wherein the enlarged 'opening within the boreof the barrel is of cross-section 5. Thesyringe of claim 4 wherein theenlarged opening is from about 1.5 to 2 times the length of the seal.

6. The syringe of claim 5 whereinthe seal is constituted of plastic.

7. The syringe of claim 5 wherein the seal is constituted of Teflon.

8. The syringe of claim 1 wherein the barrel is constituted of atransparent material, and scribed with indicia marks representative ofthe volumetric capacity of thebarrel.

9. The syringe of claim 8 wherein the volumetric cav pacity ranges fromabout 0.01 to about 5 microliters.

1. A syringe for use in separating trapped gas from liquid, and fordispensing small, pre-selected, accurately measured quantities of theliquid specimen into a media such as an analytical instrument,comprising the combination of a barrel formed by an enclosing side walldefining a central bore, the bore being of substantially uniformcross-section forward of an opening of enlarged cross-section within thebore located rearwardly within the barrel, a hollow needle mounted onthe front end of the barrel, the bore of which is in open communicationwith the bore through the barrel, a plunger reciprocably mounted withinthe bore from the rearward end of the barrel, the forward end of theplunger being traversible through the enlarged opening within the bore,and within the bore of the barrel forward of the enlarged openingitself, whereby gas trapped within a liquid to be dispersed can beseparated from the liquid, and a liquid specimen isolated from the gasfor measurement and ejection by withdrawal of the forward end of theplunger into the enlarged opening within the bore of the barrel,whereupon by forward movement of the plunger the gas is extruded throughthe annulus between the plunger and inside wall of the barrel rearwardlyof the enlarged opening, and the liquid trapped for measurement andejection by forward movement of the plunger.
 2. The syringe of claim 1wherein the enlarged opening within the bore of the barrel is ofcross-section ranging from about 1.25 to about 2 times that of the boreforward of said enlarged opening.
 3. The syringe of claim 2 wherein thediameter of the enlarged opening ranges from about 1.3 to about 1.75times the inside diameter of the bore forward of the enlarged opening.4. The syringe of claim 1 wherein the forward end of the plunger iscapped with a seal, and the enlarged opening is of greater length thanthe length of the seal.
 5. The syringe of claim 4 wherein the enlargedopening is from about 1.5 to 2 times the length of the seal.
 6. Thesyringe of claim 5 wherein the seal is constituted of plastic.
 7. Thesyringe of claim 5 wherein the seal is constituted of Teflon.
 8. Thesyringe of claim 1 wherein the barrel is constituted of a transparentmaterial, and scribed with indicia marks representative of thevolumetric capacity of the barrel.
 9. The syringe of claim 8 wherein thevolumetric capacity ranges from about 0.01 to about 5 microliters.